And this is part two of the story: Microsoft has just confirmed the next version of Windows NT (referring to it as NT for clarity's sake) will be available for ARM - or more specifically, SoCs from NVIDIA, Qualcomm, and Texas Instruments. Also announced today at CES is Microsoft Office for ARM. Both Windows NT and Microsoft Office were shown running on ARM during a press conference for the fact at CES in Las Vegas.

PAE allows you to have more than 4 GB of addressable physical memory, but you can only map them in a 32-bit address space*.

A single process can use AWE to map subsets of data in its limited address space at a time while still using more than 32-bits of physical memory. Or, in many cases, it can delegate that job to the operating system (eg. by using the OS file cache, which is not limited to the process' 4Gb limit.)

...but since developers already have issues with multiple threads I don't see this happening soon...